1. Field of the Invention
The present invention relates to a centrifugal force-based microfluidic device, and more particularly, to a centrifugal force-based microfluidic device that can be used for chemical analysis of blood, in which various kinds of biochemical reactions can take place using samples having different mixing ratios or reagents with different preparation conditions.
2. Description of the Related Art
A microfluidic structure that performs an independent function in a microfluidic device generally includes chambers that can contain a fluid, channels through which a fluid can flow, and valves that can control the flow of fluid. Such microfluidic structure can be configured by various combinations of the chambers, the channels, and the valves. An apparatus manufactured by disposing the microfluidic structure on a chip type substrate, so that a series of various biochemical reactions can be performed on a small chip, is referred to as a lab-on-a-chip.
In order to transport a fluid in a microfluidic structure, a driving pressure is necessary. The driving pressure can be capillary pressure or pressure supplied by an additional pump. Recently, a disk type microfluidic device in which a microfluidic structure is disposed on a disk-shaped platform to transport a fluid using centrifugal force and to perform a series of works has been proposed, which is referred to as a Lab CD (compact disk) or a Lab-on-a-disk. Efforts have been made to provide various disk types of microfluidic devices that can rapidly and accurately perform functions in a centrifugal force-based disk type platform.
Disk type microfluidic devices can be suitable for performing various kinds of pathological examinations. Conventional pathological examinations require a lot of work and various kinds of equipment. In order to rapidly perform an examination, skilled clinical pathologists are required. However, regardless of the skill of clinical pathologists, it is difficult to perform various kinds of examinations at the same time. In certain situations, for example in a diagnosis of an emergency patient, obtaining a rapid examination result is very important for rapid treatment of the patient. Thus, there is a need to develop an apparatus that can rapidly and accurately and simultaneously perform various pathological examinations.
In the case of a conventional blood test, large and expensive equipment, which requires a relatively large amount of blood, is used. Also, the patient must wait at least two to three days to receive the test result after taking a blood sample since the examination takes time. In order to address these problems, small and automated apparatuses for analyzing blood have been proposed. However, most of these apparatuses require that serum is separated from blood sample and then diluted before performing the tests.
An apparatus that can perform various kinds of biochemical reactions in different reaction conditions, requires the optimization of the concentrations of various reagents stored in reaction chambers and the amount of a diluent (or a dilution buffer). For example, according to U.S. Pat. No. 5,776,563, various kinds of reagents, which each are used in different reaction conditions, are required to be stored in a freeze-dried state until their use. The freeze-drying conditions of the individual reagents are different from each other, and thus, it has been proposed to use a reagent bead manufactured by optimizing the freeze-drying condition of each of the reagents. Furthermore, as it is difficult to provide samples diluted at different ratios, the dilution ratio of a sample is maintained constant, and the concentration or size of reagent beads and a size of a reaction chamber are varied to attain differently diluted samples. The necessity of frozen-dried reagent beads and of the reaction chambers of different sizes depending on the kind of reagents has complicated the design and construction of a microfluidic device.
Most of currently available biochemical reagents are stored and transported in a liquid state. Furthermore, in most cases, in order to preserve the reagents, individual reagents are preserved in separate containers, and then bring to mixing immediately before using. Therefore, there are many difficulties in providing a disk type microfluidic device that can use currently commercially available reagents.